The present invention relates to a series voltage regulator as in the introductory part of claim 1.
A conventional series voltage regulator of this type, as disclosed in U.S. Pat. No. 3,025,451 and shown in FIG. 1, is distinguished by a very low minimal series voltage drop. But as long as its input voltage is lower than that voltage level which is necessary for reaching the nominal voltage on the output side, this series voltage regulator loads with a high current the voltage source connected to its input, as shown in FIG. 2. The input current initially increases sharply in a starting range at an input voltage rising from zero, until that input voltage limit is reached at which the output voltage has reached the nominal value. In the normal operating range which is then reached, the current consumption on the input side of this series voltage regulator is many times smaller than the value which may be reached in the starting range.
Voltage sources, in particular batteries, which are designed with regard to current consumption in the normal operating range, are excessively strained in the case of undervoltage operation in the starting range. The high current consumption in the starting range may lead to these voltage sources being loaded to such a degree that the voltage they deliver does not reach the critical voltage level at which the transition to the normal operating range with normal current consumption is reached. The circuit arrangement consisting of this series voltage regulator and such a voltage source thus seizes in the starting range, resulting in a continuously high current consumption from the voltage source, i.e. rapid discharge of the battery, when a battery is being used as a voltage source.